The present invention relates to a method and apparatus for controlling the distribution of color on a textile web in a textile dyeing process.
In one known textile dyeing process, dye liquor is applied to a continuously traveling textile web by a textile padding machine. The textile padding machine includes a nip device, such as a pair of cooperating nip rollers for performing a nip operation to remove excess dye liquor and thereby control the amount of dye liquor pick up by the textile web. The traveling textile web exiting the textile padding machine has an initial moisture content which influences the eventual distribution of the color on the textile web.
In a textile dyeing process in which the textile web is to be uniformly dyed in a single color, it is especially desirable that the color distribution be as uniform as possible. In this regard, it is desirable that the color distribution be such that the color along the center of the traveling textile web be as identical as possible to the color more closely adjacent the edges of the textile web. It has been proposed to measure the moisture content of the traveling textile web following the nip operation at locations relative to the center and edge portions of the textile web. Moreover, it is known to control the nip operation in response to the measurement of the moisture content of the textile web following the nip operation. In practice, however, the distribution of color on the textile web following the textile dyeing process may be uneven despite the fact that the moisture content of the traveling textile web is substantially uniform immediately following the nip operation. This uneven distribution of color can result from different adsorption capacities of different portions of the textile web, variations in the thickness of the textile web and variations in the pre-treatment of the textile web, especially in the situation in which the textile web has been bleached prior to the textile dyeing process.
To prevent the occurrence of an uneven distribution of color, it is known to conduct a test run of a sample of the textile web to determine the color distribution characteristics of the textile web prior to the handling of the balance of the textile web. However, the travel path along which the traveling textile web is moved in the textile dyeing process can be of significant length, and can even exceed 100 meters, so that a relatively significantly large amount of textile web must be processed in the test run. The tested material must necessarily be discarded after the test run, thereby correspondingly adding to the production costs of the textile dyeing process. Another drawback of the running of a test sample of the textile web is that the test sample may not necessarily be representative of the balance of the textile web so that the adjustments of the textile padding machine indicated by the test run may not be appropriate for the actual production run of the balance of the textile web through the textile dyeing process.
Even if the test run provides accurate adjustment values for the textile padding machine, slight color variations of certain portions of the textile web ma not be noticeable until the textile dyeing process is complete and, in this event, it is often necessary to inspect the finished, dyed textile web to locate and/or identify those portions of the textile web which vary from the desired color distribution. Accordingly, the need exists for a method and apparatus for providing feedback relating to the color distribution on a textile web during a textile dyeing process so that corrective action can be taken to minimize uneven color distribution in the finished textile web.